# ---
# title: 456. 132 Pattern
# id: problem456
# author: Indigo
# date: 2021-02-02
# difficulty: Medium
# categories: Stack
# link: <https://leetcode.com/problems/132-pattern/description/>
# hidden: true
# ---
# 
# Given an array of `n` integers `nums`, a **132 pattern** is a subsequence of
# three integers `nums[i]`, `nums[j]` and `nums[k]` such that `i < j < k` and
# `nums[i] < nums[k] < nums[j]`.
# 
# Return _`true` if there is a **132 pattern** in `nums`, otherwise, return
# `false`._
# 
# **Follow up:** The `O(n^2)` is trivial, could you come up with the `O(n logn)`
# or the `O(n)` solution?
# 
# 
# 
# **Example 1:**
# 
#     
#     
#     Input: nums = [1,2,3,4]
#     Output: false
#     Explanation: There is no 132 pattern in the sequence.
#     
# 
# **Example 2:**
# 
#     
#     
#     Input: nums = [3,1,4,2]
#     Output: true
#     Explanation: There is a 132 pattern in the sequence: [1, 4, 2].
#     
# 
# **Example 3:**
# 
#     
#     
#     Input: nums = [-1,3,2,0]
#     Output: true
#     Explanation: There are three 132 patterns in the sequence: [-1, 3, 2], [-1, 3, 0] and [-1, 2, 0].
#     
# 
# 
# 
# **Constraints:**
# 
#   * `n == nums.length`
#   * `1 <= n <= 104`
#   * `-109 <= nums[i] <= 109`
# 
# 
## @lc code=start
using LeetCode

function find132pattern(nums::Vector{Int})
    stk = Int[]
    second_great = typemin(Int)
    for num in Iterators.reverse(nums)
        second_great > num && return true
        while !isempty(stk) && stk[end] < num
            second_great = pop!(stk)
        end
        push!(stk, num)
    end
    return false
end
## @lc code=end
